1. Field of the Application
The present application relates to double-flow axial turbomachines. More specifically, the present application relates to the splitter nose of a double-flow axial turbomachine, the nose splitting the incoming airflow into a primary and a secondary flow. More precisely, the present application relates to a splitter nose of an axial turbomachine provided with a de-icing system.
2. Description of Related Art
In order to optimize their thrust, turbojet engines work with several annular airflows. A primary flow passes through a compressor, a combustion chamber, and is then expanded in a turbine. A secondary flow bypasses the outside of the compressor, the combustion chamber and the turbine, and then rejoins the main flow at the outlet of the turbojet. The flows are separated by a splitter nose positioned upstream of the compressor. The shape of the nose enables the airstream entering the turbomachine to be divided and restricts entry into the compressor. Since it is located downstream of the fan blades, it is susceptible to the ingestion of foreign objects.
A splitter nose of an axial turbomachine generally comprises an external annular wall and an external stator shell. These elements comprise the guidance surfaces of the annular streams from the leading edge of the splitter nose. The geometric accuracy and the relative positioning of the guidance surfaces are guarantors of the aerodynamic stream as defined.
The relative positioning between the guidance surfaces depends on the concentricity between the annular wall and the external shell. To obtain the concentricity, it is recognised that a means of centring needs to be provided between the external shell and the annular wall. The means of centring enables the primary flow separated by the annular wall to be centred on the compressor. This promotes uniform entry of the primary flow into the low-pressure compressor and avoids vibrations being generated.
The air entering the turbomachine remains at atmospheric temperature at the splitter nose. At altitude these temperatures can drop to −50° C. In the presence of moisture, ice may form on the nose. In flight, this ice can expand and accumulate to form blocks at the tops of the compressor stator blades.
These blocks may change the geometry of the nose and influence the flow of air entering the compressor, which can reduce its efficiency. As they develop, these blocks can become very heavy. Thereafter, they may break off and be ingested by the compressor, which could damage the rotor and stator blades as they pass through.
To limit this ice formation, splitter noses are fitted with de-icers.
U.S. Pat. No. 6,561,760 B2 discloses a splitter nose for the axial compressor of a turbomachine, the nose having a de-icing system using exhaust gas. The nose is formed with an external wall and an external shell. This latter supports an annular row of stator blades. The splitter nose comprises a circular slot into which engages with an upstream edge of the external shell. The edge of the slit is machined so as to provide axial ducts in the thickness of the elements. These ducts enable the exhaust gas to circulate, which has the effect of heating the leading edge of the splitter nose. The latter is thus well protected against ice formation. However, this type of nose requires both precise and accurate machining to carry the ducts. The manufacturing costs are therefore high. Furthermore, the external wall has a solid profile that reduces thermal conduction. The external surfaces of these massive areas are thus less well de-iced. In particular, the leading edge which is in contact with a large airflow is not de-iced as effectively as the axially external surface of the annular row of blades.
Although great strides have been made in the area of splitter noses for axial turbomachines, many shortcomings remain.